1. Field of the Invention
This invention relates to a crank mechanism in a pushbutton tuner, and more particularly to a structure of a crank gear to be mounted on an end of the crank.
2. Description of the Prior Art
A pushbutton tuner is generally arranged to perform a tuning operation by rotating a crank to a predetermined extent by pushing a pushbutton, and thereby inserting a tuning core coupled to the crank into a coil. Further, in such a pushbutton tuner there is usually provided a manual tuning dial in addition to the above described tuning assembly using the pushbutton. When the drive is rotated, the crank is also rotated to the desired extent so as to tune the receiver to a station other than that selected by the pushbutton, and to perform fine adjustment during the tuning operation. In this case, if the crank is kept connected to the tuning dial during operation of the pushbutton, the load becomes so large to as disturb a smooth operation of the pushbutton. In this connection, there is often provided a clutch assembly between the crank and the tuning dial for releasing their engagement, thus reducing the load. That is, in such a conventional pushbutton tuner, the clutch assembly 1 is mounted outside a frame 2 of the tuner as shown in FIG. 1, and a clutch shaft 3 extending from the clutch assembly 1 is inserted within the frame 2 so that a clutch gear 4 fixed on one end of the clutch shaft 3 comes into meshing engagement with a sector crank gear 6 interlocking with crank bars 5. In accordance with the tendency of minimizing pushbutton tuners in size, it has been proposed to mount the clutch assembly nearer to the crank bars (within the frame, for example) thus to reduce the width of the tuner. In this case, the crank bars 5 cannot be shortened to less than a predetermined length, due to the number and the diameter of the tuning coils and the size of the pushbutton. Therefore, if the clutch assembly only is displaced deeper within the frame, the clutch gear is positioned so near to the crank bars to be disengageable with the crank gear.